Preparation of mixed unsymmetrical ethers

ABSTRACT

Salts of Group VIII, row 5 and 6, metals, e.g. ruthenium chloride, catalyze liquid phase homogenous catalysis reaction of alpha, alpha-disubstituted olefins with alcohols to produce mixed ethers. These ethers are widely used in the formation of resins, medicines, preservatives, dyes, plastics, solvents and chemical intermediates.

United States Patent 1 Holovka et al.

[ 41 PREPARATION OF MIXED UNSYMMETRICAL ETHERS [75] Inventors: John M.Holovka, Englewood; Ed-

I ward Hurley, Jr., Littleton, both of [73] Assignee: Marathon OilCompany, Findlay,

Ohio

[22] Filed: Feb. 18, 1970 [21] Appl. No.: 12,439

[52] U.S. Cl. .....260/6l1 R, 260/611 A, 260/614 AA [51] Int. Cl ..C07c41/10 [58] Field of Search ..260/611,

" A,614 A,614 AA [56] References Cited UNITED STATES PATENTS 3,479,392 11/1969 Stern et a1 ..260/614 AA 3,530,187 9/1970 Shryne ..260/614 AA3,499,042 3/ 1970 Smutny ..260/614 AA 3,489,813 1/1970 Dewhirst..260/611 A 51 Feb. 27, 1973 2,480,940 9/1949 Leum et a] ..260/614 A2,797,247 6/1957 Keith ..260/614 A 2,861,045 11/1958 Langer... 260/614 AX 2,922,822 1/1960 Beach 260/614 A 7 2,891,999 6/1959 Langer ....260/6l4A 3,547,982 12/1970 Mckeon et a1. ..260/611 A X OTHER PUBLICATIONSHandbook of Chemistry & Physics, Chemical Rubber Co., Cleveland, Ohio,44th Ed., 1962 pp. 638-641 Primary Examiner-Howard T. Mars Attorney-JackL. Hummel, Joseph C. Herring and Richard C. Willson, Jr.

[5 7 ABSTRACT 8 Claims, N0 Drawings PREPARATION OF MIXED UNSYMMETRICALETHERS BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to a method of producing mixed ethers from thereaction of alpha, alpha-disubstituted olefins and alcohols carried outin the presence of salts of ruthenium, platinum, palladium, rhodium,osmium, and iridium. Mixed ethers such as methyl-tbutyl ether andisopropyl-t-butyl ether are valuable, inter alia, in the preparation ofresins, preservatives, solvents, medicines and chemical intermediates. Anumber of methods have been employed for the preparation of such ethers.Alcohols have been added to the more reactive alkenes under theinfluences of acid catalysts to form ethers, see Royals, J. Am. Chem.

- Soc., 71, 2568 (1949). Such reactions are largely restricted to thepreparation of tert-alkyl ethers of primary alcohols, since only themore reactive alkenes and primary alcohols undergo the reaction.Secondary and tertiary alcohols do not react readily, Royals, AdvancedOrganic Chemistry, p. 380. Phenols undergo the reaction; phenol adds,for example, to isobutene to give t-butylphenyl ether.

The present invention describes a process for the preparation of mixedethers from the reaction of olefins and alcohols in the presence ofsalts of ruthenium, platinum, palladium, rhodium, osmium and iridium.

2. Description of the Prior Art Various catalysts have been used in thepreparation of mixed ethers from the reaction of olefins and alcohols.The following references are useful in defining the scope of the priorart of catalyzing the reaction. Patent Catalyst Conditions Belgian6l2,388 anion exchange Autoclave resin 60C U. S. 2,480,940 org. H-ionexchange catalyst Bnush 652,809 metal oxide H Vapor-phase reaction U. S.2,720,547 80% H,SO, 18 to +20C U. S. 2,721,222 conc. l-I,SO Autoclavel000C U. S. 2,544,392 metal oxide or Vapor-phase hydroxide reaction U.S. 3,135,807 Pb,,PMO,,

SUMMARY OF THE INVENTION General Statement of the Invention give mixedethers. The general reaction is represented by:

wherein R and R are selected from phenyl groups, mono-, di-, andtri-alkyl substituted phenyl groups havmg one to 12 carbon atoms peralkyl substituent, alkyl and cycloalkyl groups having one to 12 carbonatoms, and R" is selected from one to 12 carbon atom cycloalkyl and oneto 12 carbon atom alkyl groups. Primary and secondary alcohols arepreferred as starting materials with the primary being the mostpreferred alcohol species.

Utility of the Invention The products of this invention are useful inimproving the anti-knock qualities of fuels. See e.g., ChemicalAbstracts 42:4735 and 4736.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Starting materials The olefinstarting materials of this invention are characterized by the structurewherein R and R are selected from phenyl groups, mono-, di-, andtri-alkyl substituted phenyl groups having one to 12 carbon atoms peralkyl substituent, alkyl and cycloalkyl groups having one to 12 carbonatoms. More preferably the alkyl groups have six or fewer carbon atomsand most preferably have three or fewer carbon atoms.

The number of alkyl groups substituted on a phenyl group is preferablythree or less, more preferably two or less and most preferably one orzero. It is also preferred that there be no more than one phenyl ringsubstituted on the starting olefin.

The aromatic starting materials may include alphamethylstyrene,alpha-phenylstyrene, alpha-ethylstyrene, andalpha-methyl-para-methylstyrene.

The linear or branched-chained olefin starting materials include suchcompounds as 2-methyl-l-butene, 2-ethyl-l-butene, 2,3-dimethyl-l-butene,and isobutylene. Other substituents may be present on the R and R groupsso long as they are substantially noninterfering with the conversionreaction.

The alcohol starting materials of this invention are characterized bythe structure ROI-I, wherein R" is selected from linear orbranched-chained alkyl groups having 12 or fewer carbon atoms.Preferably the alcohol is either the primary or secondary type with theprimary alcohols being the most preferred species. Examples of suchalcohols are methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutylalcohol, and butyl alcohol. The reactions of this invention areconducted in the liquid phase. The reaction is one of homogeneouscatalysis, that is, where a catalyst, herein defined, is so dispersedwithin the reaction media that no gross interface exists between thecatalyst and the reactants.

Catalysts The catalysts of the present invention include the salts ofruthenium, palladium, platinum, rhodium, osmium, and iridium which atleast partially solubilize, preferably to a substantial degree, in thereaction media to give an active catalyst species.

Useful salts include salts of ruthenium exemplified by rutheniumchloride, osmium salts, exemplified by osmium ammonium chloride, osmiumpotassium chloride, and the like; rhodium salts exemplified by rhodiumchloride, rhodium nitrate, rhodium sulfate, and the like; iridium saltsexemplified by iridic bromide, iridic chloride, iridic iodide, and thelike. Preferred salts are those of rhodium and ruthenium. The mostpreferred anions are the chlorides which are at least partially solublein the reaction media.

For economic considerations it is important to recover the catalysts.This can be accomplished by contacting the reduced catalysts with anymaterial whose redox potential is higher than that of the catalyst. Forexample, regeneration could be effected by contact with cupric chloridewhich is reduced to cuprous chloride. Cupric chloride is a preferredoxidant because of its ready availability and the ease of reoxidationfrom the cuprous to the cupric form. Reoxidation can be accomplished bycontact with an oxidizing agent, e.g., oxygen, or more preferably, amixture of oxygen and hydrochloric acid. Other conventional methods ofregenerating the catalyst are useful for this invention and are meant tobe incorporated within its scope.

Normally the amounts of catalysts are not critical to the reaction.Excess amounts of catalysts are not preferred because of economicconsiderations but in most instances for every mole of olefin startingmaterial preferably from about 0.00001 to about 0.1 moles of catalystsare used, more preferably from about 0.0001 moles to about 0.05 molesand most preferably from about 0.001 to about 0.01 moles of catalystsare used.

The mole ratios of the olefins and alcohol starting materials are notcritical to the conversion reaction but in most instances for every moleof olefin starting material preferably from about 0.01 to about 1000moles of alcohol are used, more preferably from about 0.1 to about 100moles, and most preferably from about 5 to about moles of alcohol areused.

Temperature The homogeneous catalysis reaction is preferably conductedin the range of from about 0 to about 350, more preferably from about 50to about 250, and most preferably from about 75 to about 150C. Ingeneral, the temperature will depend upon the particular reactants andcatalyst employed as well as the pressure of the reaction. Thetemperature is preferably controlled so that the reactants remainsubstantially in the liquid phase.

Pressure Generally the reaction is conducted in a sealed vessel underautogeneous pressure, although pressure may be supplied by externalmeans and is not narrowly critical and preferably ranges from 0.01 toabout 10,000, more preferably from 1 to about 1000, and most preferablyfrom 1 to about 100 atmospheres.

Time Reaction time is not narrowly critical and will vary with thereactants, temperature and catalyst employed, but is preferably fromabout 0.1 to about 500, and more preferably from about 1 to about 200,and most preferably from about 10 to about 100 hours.

Batch or continuous basis While the examples of the present inventionare described on a batch basis, it may, of course, be practiced on acontinuous basis with continuous flows of starting materials into andwithdrawal of products from the reactor.

Additives to the reactions These reactions may be improved by carryingthem out in the present of auxiliary ligands. For instance, it has beendetermined that auxiliary ligands, such as dichloroethylene,trichloroethylene or -,P, do not interfere with the reaction. Moreover,in certain instances, the presence of one of these ligands increases thereaction rates and aids in preventing side reactions. A comparison ofexamples (1), (3), and (4) shown in the Table of Results indicates thathigher conversions are obtained when dichloroethylene or (1: is presentin the reaction mixture. Also, a comparison of examples (7) and (8)indicates that trichloroethylene has prevented the reduction of thecatalyst from occurring via a side reaction.

Additional catalysts and/or solvents may be employed to enhance the rateof reaction and yield of products. Those skilled in the art will befamiliar with such procedures.

In general, the reactions taught in this invention are carried out asfollows: A 3 oz. Fischer-Porter combustion tube containing ca. 0.04 moleof the olefin, ca. 0.4 mole of the alcohol and 0.0003 mole of catalystis equipped with a magnetic stirring bar and sealed. The tube is thenimmersed in an oil bath and stirred at a given temperature for theappropriate length of time needed to complete the reaction. The reactionmixtures are analyzed via gas chromatography, mass spec-- troscopy, nmrand ir. The products and the yields, including the molar distributionsthereof, and the selectivities are indicated in the following Table ofResults.

' TABLE or 'iissem Converllxninple Time, '1e1np., sion,

number ltenetnnts, M (Jntulyst, 1111\1. hr. (J pereent Products, M Notes1 MeOlI, 0.47; dichloroethylene, 0.05; RhCl 1120, 0.36... 16 100 -100Methyl-t-bntyl ether, 0.047.. Selectivity 08%.

isobutylene, 0.047.

.1 MeOlI, 0.655; isobutylene, 0.063 ltuCl Zi H1O, 0.3.... 10 100 63Methyl-vbutyl other, 0.037.. D0.

3 MeOH, 0.4; isobutylene, 0.030 RhCl -3 H1O, 0.33... 10 100 83Methyl-t-butyl ether, 0.034.. Do.

i 610.011, 0.525; isobutylene, 0.04; ml, Ri1C1 -3H:O, 0.35... 16 100 0Methyl-t-bntyl ether, 0.01... Selectivity 08%.

0.35 111M. partial reduction lth t0 Rh. 5. IPA, 0.26; isobutylene, 0.04RilC13'3 1110, 0.34... 67 100 lsopropyl-t-butyl ether, Selectivity 05%0.010; acetone, trace Rh+ to Rh". unknowns, 0.001.

6 IPA, 0.248; trichloroethylene, 0.0613; RhCl -3 1120,0134... 72 100Isopropyl-t-butyl ether, Do.

isobutylene, 0.0517. 0.02; acetone, trace.

7- MeOI-I, 0. 131; a-niethylstyrene, 0.03.... 111101 6 H20, 0.31. 18. 537 .Z-phenyl-Q-methoxy D0.

)ropane, 0.011.

8 MeQH, 0.283; a-niethylstyrene, 0.034; RhCl -3 1110, 0.35... 18. 5 100-11 2-phenyl-2-methoxy Selectivity 05%,

trichloroethylene, 0.030. propane, 0.014. 1110 reduction 01 (h 0. MeUII,0.47; dichloroethylene, 0.05; None. 16. 0 100 0 No reaction isobutylene,0.044.

Mole percent.

All reactions were run in Fischer-Porter combustion tubes. The productswere analyzed by nmr, 11', mass spectroscopy and gas chromatographymeans approximately.

Having thus disclosed the invention, what is claimed is:

1. In a process for the preparation of mixed ethers by the liquid phasehomogeneously catalyzed reaction of an olefin having the structure:

with alcohol having the structure R"0l-l to form 10,000 atmospheres inthe presence of a catalytic amount of a homogeneous catalyst selectedfrom chlorides of ruthenium, osmium, rhodium, iridium, palladium, andplatinum, dissolved in the reaction mixture, and in the presence of fromabout 5 to about 15 moles of alcohol per mole of olefin, and from about0.0001 to about 0.01 mole of catalyst are present per mole of olefin.

2. The process of claim 1 wherein the reaction is carried out in thepresence of auxiliary ligands selected from the group consisting ofdichloroethylene, trichloroethylene or (1: 1.

3. The process of claim 1 wherein the alkyl groups have six or fewercarbon atoms.

4. The process of claim 3 wherein the olefin is isobutylene oralpha-methylstyrene.

5. The process of claim 1 wherein R" is selected from one to 12 carbonatom cycloalkyl and one to 12 carbon atom alkyl groups.

6. The process of claim 5 wherein the ROH is a primary or secondaryalcohol.

7. The process of claim 5 wherein the R"Ol-I is rhodium chloride.

2. The process of claim 1 wherein the reaction is carried out in thepresence of auxiliary ligands selected from the group consisting ofdichloroethylene, trichloroethylene or phi 3P.
 3. The process of claim 1wherein the alkyl groups have six or fewer carbon atoms.
 4. The processof claim 3 wherein the olefin is isobutylene or alpha-methylstyrene. 5.The process of claim 1 wherein R'''' is selected from one to 12 carbonatom cycloalkyl and one to 12 carbon atom alkyl groups.
 6. The processof claim 5 wherein the R''''OH is a primary or secondary alcohol.
 7. Theprocess of claim 5 wherein the R''''OH is methyl alcohol or isopropylalcohol.
 8. The process of claim 1 wherein the catalyst is rhodiumchloride.